By: Nicole Johnson & Eric Olson CEE /15/2010

 Describe the Oscillating Water Column and how it is used to create power.  Demonstrate how OWC works.  Use OWC phenomena to estimate unknown wave properties. TPNkia96rx-xVLl39bkS0g

 An Oscillating Water Column is a device that converts wave energy into a moving air stream.  Consists of a partially sealed chamber partially submerged beneath the water’s surface. c7r69H8FOJEeFOLd1zoMC248aekWLC_Q

 Wave motion induces pressure changes beneath the column.  Pressure changes in turn cause the water level in the camber to oscillate.  Oscillating water level causes airflow in the chamber. Mn5ujfNnUdz0vlflGjBXmlTa0z_FLYyRLHH0-NbmmA

 Moving air caused by pressure differences can be used to rotate a turbine.  Wells Turbine – Rotates in the same direction regardless of the direction of the airstream. CLoWSrk-h83zgmvzJMeKKqXRLQpn9y6pA

 Materials Used: Cardboard, Straw, Playing Cards, Scotch Tape, Floss.

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 OWC ◦ Moving parts housed outside of water. ◦ Can be built near shore for easy access to power grid.  Wave Power ◦ Advantages:  Low maintenance  No greenhouse gases ◦ Disadvantages:  Initial Building cost  Eye sore

 Islay, Scottland  Installed in 2000  500kW rated

 Goal: Demonstrate the Oscillating Water Column Phenomena  Materials Used: Clear PVC Tube, Saran Wrap, Hair Tie, Bathtub, Strainer, Foot.

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 Materials Used: Original Rig, Ruler, Anemometer.

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 Wave Pressure: P(z)=-ρgz + ρgK p η  Assume Shallow Water => K p = 1  Assume: Max U occurs at τ/2  Therefore: ΔP = ρgH, ΔV=H * A 0, Δt= τ/2  Q=H*A 0 /(τ/2)  Q= A 1 *U  H= A 1 *U* (τ/2)/A 0

 Measured: ◦ A 0 = 45.6 cm. sq. ◦ A 1 =1.27 cm. sq. ◦ τ = 2 sec. ◦ U= 20 cm/s ◦ H=2.54 cm  Calculated: ◦ H= A 1 *U* (τ/2)/A 0 ◦ H=0.55 cm

 Possible Sources of Error ◦ Shallow Water Assumption ◦ Strainer Blocking Flow ◦ Oscillating Air Flow Interference ◦ Wave Reflection Interference ◦ Measurement Error ◦ Uneven wave generation

 Oscillating Water Column is an excellent method for converting wave energy to usable power.  Using OWC to indirectly measure wave height should only be considered if interfering variables can be kept to a minimum.

 de O. Flacao, A.F. Control of an Oscillating- Water-Column Wave Power Plant for Maximum Energy Production. 5/3/2002  Evans, D.V. & Porter, R. Hydrodynamic Characteristics of an Oscillating Water Column Device. 3/20/1995  Raghunathan, S. The Wells Air Turbine for Wave Energy Conversion. 1/17/1995  Wu, Chin. Wave Properties. Lecture Slides - CEE /15/2010  t.htm. 12/15/2010